1. Field of the Invention
The present invention relates generally to a method for manufacturing an array of nanostructures and a substrate with an ordered array of nanostructures, wherein the nanostructure size is controlled. More particularly, the method forms an ordered array of nanoscale holes by etching a surface through a patterned mask containing a regular array of nanoscale pores and/or deposits adatoms on the surface through the patterned mask. Also, more particularly, the substrate includes a regular array of nanoscale holes and/or a regular array of nanoclusters comprising adatoms.
2. Description of Related Art
The ability to control function by controlling size makes nanoclusters very attractive for technological applications in high-speed computing, high density data storage and display, and optical communications through devices such as the single-electron transistor and the quantum dot laser. Designs for such devices require not only sharp control of nanocluster size, but also fabrication of ordered arrays of nanoclusters and, in some cases, interconnections between clusters within the array.
As has been discussed elsewhere (for example, J.-M. Gerard, 1995), single layer quantum dot arrays have been demonstrated to have excellent optical properties such as high quantum efficiency, long radiative lifetimes, and very fast PL rise times. However, direct growth has been stymied by xe2x80x9cthe prerequisite of an ultrafine lithographic definition of the mask.xe2x80x9d
Dramatic advances have been made recently in obtaining ordered arrays of nanoclusters from liquid phase syntheses by selective precipitation and Langmuir-Blodgett techniques (Murray et al. 1993; Ohara et al. 1995; Murray et al. 1995; Whetten et al. 1996; Luedtke et al. 1996; Heath et al. 1997). Ordered arrays have also been produced using films of close-packed polystyrene spheres as deposition masks (Hulteen et al. 1995). Ensembles of individual, size-controlled InP quantum dots grown by self-assembly in molecular beam lepitaxy on a GaAs surface have emitted light of very narrow bandwidth at a wavelength determined by the size of the dots (Grundmann et al. 1995); embedded between electron-injecting and hole-injecting layers, these dots have exhibited lasing (Kirstaedter 1996). However, because they grow at randomly distributed nucleation sites on the substrate, their location is difficult to control.
From the point of view of device fabrication, it is desirable to first define the desired nanoscale array pattern directly on the substrate and then grow or deposit the nanoclusters on the patterned substrate. The nanoclusters produced preferably have diameters less than about 25 nm to show true quantum confinement behavior.
In earlier work, Heath and co-workers (1996) studied the formation of clusters in confined geometries by defining 100 and 150 nm diameter holes in a thin oxide mask over a Si wafer and then growing Ge clusters on the Si surfaces exposed in the etched holes (Gillis et al. (1992)). They observed a few clusters in each 150 nm hole at locations distributed over the bottom of the hole. A few of the 100 nm holes contained a single cluster, but difficulties with that sample precluded complete analysis. Their results showed that the confining geometry of the 150 nm hole limited the number and size of clusters growing in the hole but did not precisely control their location.
Thus, there remains a need for a method of controlling the position as well as the size of arrayed nanoclusters.
Bhatia, Suresh K. et al., xe2x80x9cFabrication of Surfaces Resistant to Protein Adsorption and Application to Two-Dimensional Protein Patterning,xe2x80x9d Analytical Biochemistry, Vol. 208, 1993, pp. 197-205.
Brock, Thomas D. et al., xe2x80x9cSulfolobus: A New Genus of Sulfur-Oxidizing Bacteria Living at Low pH and High Temperature,xe2x80x9d Arch. Mikrobiol. 84, Springer-Verlag, 1972, pp. 54-68.
Calvert, Jeffrey M. et al., xe2x80x9cDeep Ultraviolet Lithography of Monolayer films with Selective Electroless Metallization,xe2x80x9d J. Electrochem. Soc, Vol. 139, June 1992, pp. 1677-1680.
Calvert., Jeffrey M. et. al., xe2x80x9cPhotoresist channel-constrained deposition of electroless metallization on ligating self-assembled films,xe2x80x9d J. Vac. Sci. Technol. B, Vol 6, November/December 1994, pp. 3884-3887.
Clark et al., U.S. Pat. No. 4,728,591, issued Mar. 7, 1986.
Clark et al., U.S. Pat. No. 4,802,951, issued Feb. 7, 1989.
Deatherage, J. F. et al., xe2x80x9cThree-dimensional Arrangement of the Cell Wall Protein of Sulfolobus acidocaldarius,xe2x80x9d J. Mol. Biol., Vol. 167, 1983, pp. 823-852.
Douglas, Kenneth et al., xe2x80x9cNanometer Molecular Lithography,xe2x80x9d Appl. Phys. Lett., Vol. 48, No. 10, Mar. 10, 1986, pp. 676-678; correction in Appl. Phys. Lett., Vol. 48, No. 26, Jun. 30, 1986, p. 1812.
Douglas, Kenneth et al., xe2x80x9cTransfer of Biologically Derived Nanometer-Scale Patterns to Smooth Substrates,xe2x80x9d Science, Vol. 257, Jul. 31, 1992, pp. 642-644.
Gxc3xa9rard, Jean-Michel et al., xe2x80x9cProspects of High-Efficiency Quantum Boxes Obtained by Direct Epitaxial Growth,xe2x80x9d in Confined Electrons and Photons: New Physics and Applications, Elias Burstein and Claude Weisbuch, eds., Plenum Press, New York, 1995, pp. 357-381.
Gillis, H. P. et al., xe2x80x9cLow-energy electron beam enhanced etching of Si(100)-(2xc3x971) by molecular hydrogen,xe2x80x9d J. Vac. Sci. Technol B, Vol. 10, No. 6, November/December 1992, pp. 2719-2733.
Gillis, H. P. et al., xe2x80x9cLow energy electron-enhanced etching of Si(100) in hydrogen/helium direct-current plasma,xe2x80x9d Appl. Phys. Lett., Vol 66, No. 19, May 8, 1995, pp. 2475-2477.
Gillis et al., U.S. Pat. No. 5,917,285, issued Jun. 29, 1999.
Grogan, Dennis W., xe2x80x9cPhenotypic Characterization of the Archaebacterial Genus Sulfolobus: Comparison of Five Wild-Type Strains,xe2x80x9d J. Bacteriology, Vol. 471, No. 12, December 1989, pp. 6710-6719.
Grundman, M. et al., xe2x80x9cUltranarrow Luminescence Lines from Single Quantum Dots,xe2x80x9d Phys. Rev. Lett., Vol. 74, No. 20, May 15, 1995, pp. 4043-4046.
Harrison, Christopher et al., xe2x80x9cLithography with a mask of block copolymer microstructures,xe2x80x9d J. Vac. Sci. Technol. B, Vol. 16, No. 2, March/April 1968, pp. 544-552.
Heath, J. R. et al., xe2x80x9cSpatially Confined Chemistry: Fabrication of Ge Quantum dot Arrays,xe2x80x9d J. Phys. Chem., Vol. 100, 1996, pp. 3144-3149.
Heath, James R. et al, xe2x80x9cPressure/Temperature Phase Diagrams and Superlattices of Organically Functionalized Metal Nanocrystal Monolayers: The Influence of Particle Size, Size Distribution, and Surface Passivant,xe2x80x9d J. Phys. Chem. B, Vol. 101, 1997, pp. 189-197.
Hulteen, John C. et al., xe2x80x9cNanosphere lithography: A materials general fabrication process for periodic particle array surfaces,xe2x80x9d J. Vac. Sci. Technol. A, Vol. 13, No. 3, May-June 1995, pp. 1553-1558.
Jackman, Rebecca J. et al., xe2x80x9cFabrication of Submicrometer Features on Curved Substrates by Microcontact Printing,xe2x80x9d Science, Vol. 279, Aug. 4, 1995, pp 664-666.
Kim, Enoch et al., xe2x80x9cCombining Patterned Self-Assembled Monolayers of Alkanethiols on Gold with Anisotropic Etching of Silicon to Generate Controlled Surface Morphologies,xe2x80x9d J. Electrochem. Soc., Vol. 142, No. 2, February 1995, pp. 628-632.
Kirstaedter, N. et al., xe2x80x9cGain and differential gain of single layer InAs/GaAs quantum dot injection lasers,xe2x80x9d Appl. Phys. Lett., Vol. 69, No. 9, Aug. 26, 1996, pp. 1226-1228.
Kumar et al., xe2x80x9cFeatures of gold having micrometer to centimeter dimensions can be formed through a combination of stamping with an elastomeric stammp and an alkanethiol xe2x80x9cinkxe2x80x9d followed by chemical etching,xe2x80x9d Appl. Phys. Lett., Vol. 63, No. 14, Oct. 4, 1993, pp. 2002-2004.
Kumar, Amit et al., xe2x80x9cPatterning Self-Assembled Monolayers: Applications in Materials Science,xe2x80x9d Langmuir, Vol. 10, 1994, pp. 1498-1511.
Lembcke, G. et al., xe2x80x9cImage analysis and processing of an imperfect two-dimensional crystal: the surface layer of the archaebacterium Sulfolobus acidocaldarius re-investigated,xe2x80x9d J. Microscopy, Vol. 161, Pt. 2, February 1991, pp. 263-278.
Lercel, M. J. et al., xe2x80x9cSub-10 nm lithography with self-assembled monolayers,xe2x80x9d Appl. Phys. Lett., Vol. 68, No. 11, Mar. 11, 1986, pp. 1504-1506.
Luedtke, W. D. et al., xe2x80x9cStructure, Dynamics, and Thermodynamics of Passivated Gold Nanocrystallites and Their Assemblies,xe2x80x9d J. Phys. Chem., Vol. 100, No. 32, Aug. 8, 1996, pp. 13323-13329.
Martin et al., U.S. Pat. No. 5,882,538, issued Mar. 16, 1999.
Martin et al., U.S. Pat. No. 6,027,663, issued Feb. 22, 2000.
Martin et al., U.S. Pat. No. 6,013,587, issued Mar. 7, 2000.
Michel, H., et al., xe2x80x9cThe 2-D Crystalline Cell Wall of Sulfolobus Acidocaldarius: Structure, Solubilization, and Reassembly,xe2x80x9d in Electron Microscopy at Molecular Dimensions: State of the Art and Strategies for the Future, Wolfgang Baumeister and Wolrad Vogell, eds, Springer-Verlag, Berlin, 1980, pp. 27-35.
Moore, Jon T. et al., xe2x80x9cControlled morphology of biologically derived metal nanopatterns,xe2x80x9d Appl. Phys. Lett., Vol. 71, No. 9; Sep. 1, 1997, pp. 1264-1266.
Murray, C. B. et al., xe2x80x9cSynthesis and Characterization of Nearly Monodisperse CdE (E=S, Se, Te) Semiconductor Nanocrystallites,xe2x80x9d J. Am. Chem. Soc., Vol. 115, 1993, pp. 8706-8715.
Murray, C. B. et al., xe2x80x9cSelf-Organization of CdSe Nanocrystallites into Three-Dimensional Quantum Dot Superlattices,xe2x80x9d Science, Vol. 270, Nov. 24, 1995, pp. 1335-1338.
Ohara, Pamela C. et al., xe2x80x9cCrystallization of Opals from Polydisperse Nanopartaicles,xe2x80x9d Phys. Rev. Lett., Vol. 75, No. 19, Nov. 6, 1995, pp. 3466-3469.
Ozin, Geoffrey A, xe2x80x9cMorphogenesis of Biomineral and Morphosynthesis of Biomimetic Forms, Acc. Chem. Res., Vol. 30, 1997, pp. 17-27.
Pearson, D. H. et al., xe2x80x9cNanochannel Glass Replica Membranes,xe2x80x9d Science, Vol. 270, Oct. 6, 1995, pp. 68-70.
Pum, Dieter et al., xe2x80x9cAnisotropic crystal growth of the S-layer of Bacillus sphaericus CCM 2177 at the air/water interface,xe2x80x9d Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol. 102, 1995, pp. 99-104.
Pum, Dieter et al., xe2x80x9cMolecular Nanotechnology and Biomimetics with S-Layers,xe2x80x9d in Crystalline Cell Surface Proteins, Academic Press and R. G. Landes Co., Austin, Tex., 1996, pp. 175-209.
Sleytr, Uwe B. et al., xe2x80x9cCrystalline Surface Layers on Bacteria,xe2x80x9d Ann. Rev. Microbiol., Vol. 37, 1983, pp., 311-319.
Sleytr, Uwe B. et al., xe2x80x9cTwo-Dimensional Protein Crystals (S-Layers): Fundamentals and Application Potential,xe2x80x9d Mat. Res. Soc. Symp. Proc., Vol. 330, 1994, pp. 193-199.
St. John, Pamela M. et al., xe2x80x9cMicrocontact printing and pattern transfer using trichlorosilanes on oxide substrates,xe2x80x9d Appl. Phys. Lett., Vol. 68, No. 7, Feb. 12, 1996, pp. 1022-1024.
Taylor, K. A. et al., xe2x80x9cStructure of the S-layer of Sulfolobus acidocaldarius,xe2x80x9d Nature, Vol. 299, Oct. 28, 1982, pp., 840-842.
Weiss, Richard L., xe2x80x9cSubunit Cell Wall of Sulfolobus acidocaldarius,xe2x80x9d J. Bacteriology, April 1974, pp. 275-284.
Whetten, Robert L. et al., xe2x80x9cNanocrystal Gold Molecules,xe2x80x9d Adv. Mater., Vol. 8, No. 5, 1996, pp. 428-433.
Wilbur, James L. et al., xe2x80x9cMicrofabrication by Microcontact Printing of Self-Assembled Monolayers,xe2x80x9d Adv. Mater., Vol. 6, No. 7/8, 1994, pp. 600-604.
The present invention, provides a method for producing substrates, wherein single nanoclusters are formed in regular arrays. By etching holes an order of magnitude smaller in diameter than those of Heath et al. (1996), we have observed the formation of a single nanocluster in each hole when Ti adatoms are deposited on a Si substrate that has been etched to define an array of nanometer-sized holes. The symmetry and lattice constant of the array, as determined by atomic force microscopy (AFM), are identical to those of the etched holes, demonstrating that these extremely small holes control the position as well as the number of 5 clusters grown in each hole.
It is an object of the present invention to provide new nanopattern mask materials which allow formation of nanostructures having controlled diameters without the slow throughput of electron beam lithography and the high cost of X-ray lithography.
It is another object of the present invention to provide new nanopattern masks which intrinsically contain mesoscopic scale openings.
It is a further object of the present invention to provide a process for creating nanostructures combining the steps of obtaining a biologically derived mask, transferring the mask pattern to a substrate using low-damage dry etching under conditions that control the size of the transferred pattern features, and initiating cluster growth by adatom deposition.
It is still another object of the present invention to achieve massively parallel processing in fabricating an ordered and precisely positioned array of nanoclusters of controlled size.
It is yet another object of the present invention to create arrays of holes having controlled diameters small enough to induce the formation of nanoclusters which exhibit quantum confinement behavior without causing adjacent lattice damage to the substrate.
One embodiment of the present invention comprises a method for preparing masks having ordered arrays of nanoscale pores. The method comprises the steps of providing a mask template having a structure including an ordered array of nanoscale pores, mounting the mask template on a substrate, and at least partially coating the mask template with an etch/deposition mask such that the etch/deposition mask has a pre-selected effective pore diameter different from the pore diameter of the mask template. Preferably, the mask template is of biological origin. The providing step may comprise culturing an organism which synthesizes a material having a structure suitable for use as the mask template and isolating the cultured material. A preferred organism is a bacterium of the genus Sulfolobus.
The mounting step may comprise forming a suspension of a plurality of the mask templates in a liquid, applying the suspension to a surface of the substrate, and removing the liquid from the surface. A surfactant may be added to alter the ability of the liquid to wet the surface.
The coating step may comprise forming the etch/deposition mask by applying a coating from a direction other than normal to said mask template. The coating step may comprise applying a coating from a direction selected to provide an annulus of said coating within the pores of said mask template or applying a coating from a direction selected to provide a larger effective pore diameter in the etch/deposition mask than the diameter of the pores of the mask template.
An etch mask formed in accordance with the present invention, having ordered arrays of nanoscale pores, may comprise a material selected from titanium, chromium, vanadium, tungsten, and combinations thereof.
In yet another embodiment, the present invention comprises a method for fabricating ordered arrays of nanoscale features. The method comprises the steps of providing a mask template having a structure including an ordered array of nanoscale pores, at least partially coating the mask template with an etch mask material to form an etch mask having a pre-selected effective pore diameter different from the pore diameter of the mask template, and using the etch mask for performing at least one operation on a substrate, wherein the operation is selected from depositing material on the substrate and removing material from the substrate based on the locations of the pores. Preferably, the mask template is obtained from bacteria of the genus Sulfolobus. The etch mask may comprise a material selected from titanium, chromium, vanadium, tungsten, and combinations thereof. The mask template and the etch/deposition mask may have a pore spacing between about 3 and about 30 nm, and the nanoscale features may have a diameter varying from about 1 to about 30 nm. The coating step may comprise controlling the effective pore diameter of the etch/deposition mask by applying a coating from a direction other than normal to the mask template. The direction may be selected to provide an annulus of said coating within the pores of said mask template or to provide a larger effective pore diameter in the etch/deposition mask than the diameter of the pores of the mask template, and the method comprises the additional step of removing material from around the pores of the mask template.
In another embodiment, the present invention comprises an ordered array of nanoscale features, formed by the method comprising the steps of providing a mask template having a structure including an ordered array of nanoscale pores, at least partially coating the mask template with an etch mask material to form an etch mask having a different effective pore diameter than the pore diameter of the mask template, and using the etch mask for performing at least one operation on a substrate, wherein the operation is selected from depositing material on the substrate and removing material from the substrate based on the locations of the pores.
In another embodiment, the present invention comprises an ordered array of nanoscale features, formed by the method comprising the steps of providing a patterning mask having a structure including an ordered array of nanoscale pores, at least partially coating the patterning mask with an etch mask material to form an etch mask having a different effective pore diameter than the pore diameter of the patterning mask, and using the etch mask for performing at least one operation on a substrate, wherein the operation is selected from depositing material on the substrate and removing material from the substrate based on the locations of the pores.